Process for the purification of terephthalic acid

Disclosed is a process for the purification of a crude terephthalic acid product contaminated with up to 10% by weight of partially oxidized impurities including p-toluic acid and 4-carboxybenzaldehyde, comprising the steps of dissolving the crude product in water by heating up to a temperature at least about 5 DEG C. higher than necessary for having the resulting solution saturated with terephthalic acid; cooling the resulting solution down to a temperature not lower than about 185 DEG C. to precipitate purified crystals; recovering the purified crystals by solid-liquid separation at a temperature not lower than that used for the precipitation of the purified crystals; and washing the recovered crystals by contacting with water at a temperature which is at least as high as the temperature of the recovery step.